This invention relates to improvements in apparatus and method for molding rubber articles and more particularly to means for preparing uncured rubber in order to accelerate the molding process, reduce natural waste, reduce flash and improve product quality and consistency.
Heretofore, uncured rubber was preformed and heated on a warm-up mill before being transferred to the molding press. In order to speed the molding process, the warm-up mill has been placed adjacent to the molding press (U.S. Pat. No. 3,898,314). However, during this warm-up step nonuniform heating occurs. Additionally, the cost and space required by the warm-up mill and the fact that it can not run automatically renders it uneconomical in production.
In the preferred embodiment of the present invention, rubber stock is prepared for molding by plasticizing the raw stock through an extruder to obtain homogenous dispersion and temperature. The extruder utilizes both mechanical compression and electrical heating coils to impart an elevated temperature. Further, while in this plasticized state, an accurate amount of prepared rubber is metered for input to the molding press. With this process production is increased, waste and flash are reduced, and product quality and consistency are improved.